In order to protect electrical connectors from adverse environmental conditions such as moisture, insects, dirt, and corrosion deposits, appropriate seals must be incorporated into their construction. Known connector seals include grommets or similar types of compression seals, heat shrinkable sealing sleeves, greases, epoxies, and gels.
Gel sealants provide several advantages over other known sealing devices and their use with electrical connectors is well known. Gel sealants also provide a way to seal a multi-conductor connector so that the connector can be assembled and sealed, prior to the electrical contacts being inserted into the connector that retains the seal. This arrangement allows a single connector to be used with various arrangements of electrical contacts.
The use of a gel sealant in an electrical connector also allows the electrical contacts within the connector to be removed and re-inserted after the connector has been sealed. This can be accomplished without compromising the integrity of the seal, and without significant degradation of the sealing material. Thus, an electrical contact can be inspected or repaired and the seal will continue to perform after the contact is reinserted.
The use of a gel sealant in an electrical connector also allows the electrical connector to be designed prior to knowing the number of electrical contacts actually needed. Such a generic connector may be utilized in order to allow for various product options or customer configurations. Thus, a connector can be chosen prior to finalizing a customer's specifications and allows a single design to be used for many different connector configurations.
Known gel sealants are effective at sealing electrical connectors. For example, U.S. Pat. Nos. 5,529,508, 5,588,856, and 5,934,922 each describes the use of gel sealants in electrical connectors. The details of each of these patents is hereby incorporated by reference into the present disclosure.
In order to function properly, a gel sealant must be sufficiently compressed within the connector components. This compression allows the gel sealant, which has fluid-like and elastic properties, to readily fill any voids or cracks in the connector. When compressed, the gel sealant wets the surfaces of the connector, displacing any moisture or air, and forms a bond with the connector surfaces.
Experience has shown that gel sealants perform best when they are placed under an initial compression pressure of approximately 1 bar. This initial compression strikes a balance between the viscous and elastic properties of the gel so that the gel will readily fill all voids and cracks within the connector while at the same time allowing the gel to tack against the surfaces of the connector.
Typically, the connector housing and connector cap each have an array of through holes that align the electrical contacts. Since electrical pins or connectors are inserted through these through holes, the gel sealant must contact them. Because there may be a variance in the number of through holes actually used, the surface area that the gel sealant contacts may also vary, and the pressure that the gel grommet requires to effectively seal the connector will change from connector to connector.
While design guides and rules of thumb have been developed for estimating the required pressure on a gel sealant to maintain an effective seal, these estimations are far from exact. Current procedures advise that a prototype connector be manufactured or that stereo lithography be used so that an actual design can be tested. The time and cost associated with these procedures are prohibitive in many applications.
Further, the large tolerances that are present in the manufacture of gel sealants yields a +/−15% variance in the gel's thickness. Thus, even after a new connector is designed and the connector positions are determined, a variation in the gel sealant thickness may result in a wide range of pressures that are required to properly seal the connector. Since known connectors are generally fixed in their positioning relative to the gel sealant, a proper seal may not result if the gel thickness varies too much.